Method of purifying anthracene and other substances



Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE FRANCIS EDWARD CISLAK, OF INDIANAPOLIS, INDIANA,'ASSIGNOB TO' PETER C. V

' REILLY, OF INDIANAPOLIS, INDIANA METHOD OF PURIFYING ANTHRACENE'AND OTHER SUBSTANCES .No Drawing. Application filed July 7,

My invention relates to the purification of anthracene, and incidentally to the concentration and purification of phenanthrene and carbazole. I

' It is the object of my invention to effect the purification of anthracene, in a simple manner, and as an incident thereto to obtain at the same time concentrated phenanthrene and carbazole.

As anthracene is obtained in the crude form from coal-tar, and even when it IS fairly well purified, it has mixed with it varying quantities of contaminants which are separated with it from such coal-tar. The main ones of these contaminants are methyl anthracene, benzo-carbazole, paraflin, phenanthrene, and carbazole; of which the last two occur in the largest portions. These contaminating substances of anthracene have heretofore been rather difficult to separate from it, and such separation has involved rather large expense.

I have discovered that there is a marked differential solubility of anthracene on the one hand and phenanthrene and carbazole on the other hand, in 4-hydroxy-4-methyl-2- pentanone. This differential solubility I have found to be particularly marked" at a temperature in the neighborhood of 25 C. so At that temperatureand thereabouts, I have found that anthracene is materially less soluble in 4-hydroxy-4-methyl-2-pentanone than are phenanthrene and carbazole.

By taking advantage of this differential a5 solubility, I have found it possible to purify anthracene simply and inexpensively. For instance, by starting with a crude anthracene that contains only 15 to 20% of anthracene, I have found that by two recrystallizations from this solvent I am able to obtain an anthracene of about 95% purity. The number of recrystallizations used depends upon the composition of the ori inal product, and on the extent of purification desired. The following is an example of this purification:

One part of a crude anthracene, of between and purity, is dissolved in five parts of 4-hydroxy-4-methyl-2-pantanone, at 50 a temperature of about 100 C. When solu- 1930. Serial No. 466,047.

tion is complete, the solution is allowed to cool, desirably to about 25 0., or somewhere in the range from15 to 35 C.; upon which cooling certain crystals appear. These crystals are separated from the solution, as 55 for example by filtering, centrifuging, or decanting. The crystalline mass is an anthracene of about 8 l% purity; and the yield is usually about -95% of the theoretical.

For many uses, the anthracene just .obe0 tain-ed is-of sufiicient purity, without further purification.v However, if further purification isdesired, the product of the firstrecrystallization is again dissolved in le-hydroxy-4-methyl-2-pentanone, desirably by as heating to C. This time it is usually necessary to use more of the solvent, about 10 parts, in order to obtain complete solution. When solution is complete, the solution is allowed to cool as before, desirably 7o to about 25 C. or within-10 thereof on either side; and crystals appear. These are separated from the solution as before, yielding an antharcene of about 94-96% purity. The yield 'on this second recrystallization is 75 usually about 899l% of the theoretical.

If still further purification is desired, the process of dissolving and recrystallizing may be repeated as often as desired. Generally speaking, the purity'of the anthracene is inso creased at each recrystallization, while the yield is decreased.v f p The purities and yields which are given 7 above are given as examples only, and the inventionis in no way limited to them. 8-5

In performing this process ofalternate dis- J solving and recrystallizing, the phenanthrene and carbazole which were present as contaminants of the anthracene remain for most part in solution, on account of the differential sole0 ubility already referred to. These may be separatedfrom the solvent, asfor example bydistillation or crystallization; and'at the same time the solvent is recovered for further use. The phenanthrene and the car- .9

bazole are thus obtained in more concentrated form than they were originally. n Instead of obtaining the fractional crystallization by'varying the temperature, it is possible to obtain it by distillation or partial [10a 7 evaporation. I believe that it is best to carry out the partial evaporation in the neighborhood of 25 0., by evaporating under vacuum, as there is a marked differential solubility at that temperature and in the vicinity thereof. If such recrystallization is obtained by evaporation, the anthracene comes down in purer form at the higher volume, and decreases in purity as the volume of the solution is decreased; so that it is desirable to remove the crystals of anthracene that are formed before the evaporation has been car ried too far, in order to obtain the desired purification of the anthracene.

It is also possible, although less desirable, to obtain the separation of theanthracene from the contaminating phenanthrene and carbazole, by grinding the crystals of the mixed product to fine form, and then extracting with 4-hydroXy-4-methyl-2-pentanone. If this is done carefully at about 25 or 30 (1, with not more than five or six parts of the solvent and with efficient stirring, it is found that the contaminants, especially phenanthrene and carbazole, are to a large extent dissolved by the solvent, while most of the anthracene remains undissolved in a purified form.

However, I prefer the process involving dissolving the anthracene to be purified in a suflicient quantity of 4-hydroXy-4-methyl-2- pentanone to obtain substantially complete solution at a rather high temperature, and then lowering the temperature of the solution to obtain recrystallization of the anthracene while leaving most of the contaminants in solution.

In thus purifying the anthracene of phenanthrene and carbazole by reason of their differential solubility, I also purifyit to a large extent from its other contaminants, which are present in smaller quantities, even though their solubility in this solvent is not so different from that of anthracene as is that of phenanthrene and carbazole.

This same solvent may also be used in the same way to'separate anthracene from mixtures of it with other substances havinga different solubility in it from that of anthracene.

I claim as my invention 1-- 1 The process of purifying anthracene, which consists in treating with 4-hydroXy-4- methyl-Q-pentanone anthracene which contains contaminants that are separated with it from coal-tar, and utilizing the solventzole, and separating the purified anthracene from the solution.

3. The process of purifying anthracene, which consists in dissolving in -hydroxy-t metl1yl-2-pentanone at an elevated temperature anthracene which contains contaminants that are separated with it from coal-tar, and producing recrystallization of anthracene from. the solution at a lower temperature.

4. The processof purifying anthracene, which consists in dissolving in 4-hydroXy-tmethyl-2-pentanone anthracene which contains contaminants that are separated with it from coal-tar, and producing recrystallization of anthracene from the solution.

5. The method of concentrating carbazole and phenanthrene, and substantially separating them from anthracene, which consists in dissolving a mixture of these materials in 4e-hydroxy-4-methyl-2-pentanone, and recrystallizing anthracene therefrom.

6. The method of purifying anthracene from contaminants which atlow tempera tures are more soluble than it is in 4-hydroxyt-methyl-Q-pentanone, which consists in dissolving such contaminated anthracene in a sufficient amount of 4-hydroXy-4-methyl-2- pentanone at an elevated temperature to obtain complete solution, and lowering the temperature of the solution to cause recrystallization therefrom of purified anthracene.

7. The method of purifying anthracene from contaminants at about 25 C. are more soluble than it is in 4-hydroXy-4-methyl-2- pentanone, which consists in dissolving such contaminated anthracene in l-hydroxylmethyl-Q-pentanone at about 100 C., and then cooling the solution to about 25 C. to

cause the recrystallization therefrom of purified anthracene.

8. The method of purifying crude anthracene, which consists in treating said crude anthracene with thydroxy-t-methyl-Q-pentanone to obtain'a purified anthracene in solid form and a solution of the contaminants, and separating the purified anthracene from the solution. 7

9. The use of 4-hydroxy-4c-methyl-2-pentanone as a selective solvent to purify anthracene from phenanthrene and carbazole.

Inwitne'ss' whereof, I have hereunto set my hand at Indianapolis, Indiana, this 3d day of July, A. D; one thousand nine hundred and thirty.

FRANCIS EDl/VABD CISLAK.

power of said solvent to produce separation of purified anthracene from such contaminants.

2. The process of purifying anthracene from phenanthrene and carbazole, which consists in treating a mixture of such substances with 4-hydroXy-4- methyl-2 -pentanone to obtain a purified anthracene'in solid. form. and

a solution of said phenanthrene and carba- CERTIFICATE OF CORRECTION.

Patent No. 1,879,090 September 27, 1932.

FRANCIS EDWARD GISLAK.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 98, claim 7, after "contaminants" insert the word which; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of November, A. D. 1932.

M. J. Moore,

(Seal) Acting Commissioner of Patents. 

